1. Technical Field
The present invention relates to an infrared detection circuit, a sensor device, and an electronic instrument.
2. Related Art
A known conventional infrared detection circuit uses a pyroelectric element. A human body emits infrared radiation at wavelengths in a vicinity of 10 μm, and the conventional infrared detection circuit can detect the existence of a person or acquire temperature information regarding a person in a non-contact fashion by detecting such radiation. Thus, this kind of infrared detection circuit can be used to detect intruders and to measure physical quantities.
A conventional infrared detection circuit disclosed in Japanese Laid-Open Patent Publication No. 59-142427 is configured to read a pyroelectric current from a pyroelectric element while cyclically exposing and interrupting the exposure of the pyroelectric element to an infrared radiation by using a mechanical chopper.
Another conventional infrared detection circuit disclosed in Japanese Laid-Open Patent Publication No. 2006-3301 is a dielectric barometer type detection circuit not requiring a chopper. This detection circuit utilizes a change of a capacitance value of a capacitor caused by a temperature increase resulting when the detection circuit is exposed to infrared radiation.
Another conventional infrared detection circuit disclosed in Japanese Laid-Open Patent Publication No. 2008-26249 serves to read a charge a plurality of times in order to increase a sensitivity and it includes an integration circuit comprising an operational amplifier, a reset switch, and an integration capacitor. Also included are four switches and a capacitor (pyroelectric element) configured such that its capacitance value changes in accordance with an amount of infrared radiation it is exposed to.